ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume II-5/W3, 2015 25th International CIPA Symposium 2015, 31 August – 04 September 2015, Taipei, Taiwan

TOPOGRAPHY RESTORATION OF HISTORIC CITY RESEARCH

Lee Sung hoa, Han Dong soob

a Doctor’s course completion, Hanyang University Seoul - [email protected] b Prof., Hanyang University Seoul - [email protected]

Commission I I, WG I I/3

KEY WORDS: Restoration, GIS, Buyeo, Sabi Capital City, Baekje

ABSTRACT:

The preservation of historic cities requires a balance between conservation and development because the urban structures of the old and new city are interwoven on same space. Existing restoration plans rely on old records and excavation reports and are based on the present topography. However, historic cities have undergone significant natural and anthropogenic topographic changes such as alluvial sediment accumulation and uneven terrain construction. Therefore, considering only the present topography is misleading. Thus, to understand a historic city’s structure more appropriately, it is necessary to comprehend the ancient geographic environment. This study provides an analysis and GIS visualization of the ancient topography of a historic city, Sabi capital city of the Baekje Dynasty, which collapsed 1,500 years ago.

1. INTRODUCTION 2. NECESSITY AND METHOD OF TOPOGRAPHIC RESTORATION FOR HISTORIC CITIES The historic city of Buyeo is located in the central Korean Peninsula and was the Sabi capital city (538 – 660 AD), the last Topographic restoration is necessary for three reasons. First, it of the Baekje Dynasty (百濟, 18 BC – 663 AD). This was a provides interdisciplinary data, which complement current golden age for the city in every fields: refined architecture; ineffective efforts. East Asian historic cities differ from those in craft; art; religion; international exchange with China, Japan, Europe, such as Rome, that have been researched since the 15th India, and other southeast Asia ancient countries; and powerful century. Existing methods would require significant time and royal dominion. However, despite the historicity of the Baekje effort to produce actual results for the historic cities of East Dynasty’s splendid civilization, Buyeo’s urbanization since the Asia. Therefore, alternative sources are required to complement 1970s was undiscerning. In the middle 1990s, as the importance the excavation data. Second, topographic restoration allows of Buyeo historic city was highlighted, the conservation versus reinterpreting the excavation findings. Because topography has development dilemma became an issue. The historic city significantly changed during the development and management legislation includes the conservation of ruins, modernization of the city, studies based solely on the present which were discovered underneath the present city, thus topography lead to misinterpretation of the value and stature of restricting further construction. Excavation has intermittently the excavated ruins. Hence, to appropriately reconstruct the progressed for about 15 years, dotting the city. Yet, the historic historic city, it is necessary to understand the ancient city is only partially reconstructed through these efforts. The topography. Third, topographic restoration provides information authorities vaguely predict that almost all major ruins are on land use during ancient times, which enables creating more located just under the downtown of present Buyeo, where there efficient excavation plans. For example, the ancient streams’ are many modern structures. However, the lack of accurate higher flooding limit and the buildable area are separated. estimates results in inefficient conservation and development, The topographic restoration procedure is divided into four and significantly delays the historic city’s preservation. For the stages adapted to the situation, period, and particular features of past 10 years, on the basis of the limited archaeological data the historic city under study. available, scholars postulated that the ancient urban structure • Preparatory stage: artificial topography changes check and produced a city with well-appointed gridiron roads. However, restoration range set. the evidence from the modern excavations continuously • Data collection and computerization stage: humanistic data contradicts this theory. This study proposes the reconstruction (e.g., old records, legends, old maps, locality names, local of the ancient topography as a necessary tool in historic city development history, survey, excavation, distribution chart of restoration. The historic city of Buyeo is treated as an example, the excavation site), scientific data (e.g., geological features, focusing on restoring the actual topography 1,500 years ago. hydrography, seawater activity, climatic changes, natural Furthermore, the urban structure of the ancient capital city, Sabi, disasters, vegetation changes, ancient agricultural techniques, is investigated by analyzing this restored topography. ancient vessels), data computerization (assimilating and preparing data for the geographic information system). • Data analysis stage: comparative analysis of disparate data, deduction of natural topographic change order, and rules and hypothesis of topography restoration.

This contribution has been peer-reviewed. The double-blind peer-review was conducted on the basis of the full paper. doi:10.5194/isprsannals-II-5-W3-301-2015 301

ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume II-5/W3, 2015 25th International CIPA Symposium 2015, 31 August – 04 September 2015, Taipei, Taiwan

• Restoration stage: establishing the appropriate restoration almost no error. This map is compared with the present one to method (according to the particular characteristics of each identify the natural topographic changes until today, and then historic city and considering the local geographic factors such used as the base map to restore the ancient topography. In this as plains, mountains, and streams); Table 1 provides these study, the entire putative old city and the riverside area are features for the case study of Buyeo, adjusted to the restored, which parts were most radically altered. restoration of the ancient topography 1,500 years ago.

Factor Procedure Detail method

• Differences in altitude between the present and old topography (extracted data from excavation reports). Earth surface • Order of natural topographic changes changes (comparative analysis based on geological features and the known altitude values for the ancient Plains topography). & Primary Mount topographic • Creating a 3D topographic model ains model (standard using the base map (e.g., AutoCAD, time) ArcGIS Spatial analysis tool). Modifying each XY-isometric point on Secondary • the primary model (the present altitude topographic to the ancient). model (restoration • Recreating the 3D topographic model time) using the modified data (with GIS interpolation or an alternative method). • Reviewing overall river gradient of target area. Figure 1. Base map and the restoration boundary Gathering clues related with ancient • water level (river bank, docking facility, old records, local legend etc.) 3.2 Ancient topography analysis Ancient river • Grasping water surface level value of boundaries the clue (restoration time) and applying Remains each point through calculating the river gradient value. Rivers & • Appling each ancient water surface Granite Strea data to 3D topography model both ms normal and flood season. Assuming a normal water level and Application of • flood season for the ancient river. ancient water system data to • Estimating the ancient water level by the model applying its altitude to the 3D model (considering entire geomorphic grades).

Ancient stream • Restoring steams using the 3D way trace restoration model (ArcGIS hydrology tool). Table 1. The ancient topographic restoration process by geographic factors Alluvial soil

3. BUYEO ANCIENT TOPOGRAPHIC RESTORATION Figure 2. Geographical feature and remains 3.1 Restoration range and base map setting Until now, the large plain area of the historic city of Buyeo was Buyeo has significantly transformed since the 1970s to the great regarded as a single geographical feature, covering many major plain area observed today. In the 1970s, the entire area was flat, ancient remains. However, it actually includes two different and during the 1980s, several environmental changes occurred: geological units, granite and alluvial soil. The ancient a dam on the upper river, an estuary dam on the lower river, topographic data acquired from relevant excavation reports are riverbanks, large bridges, sand collection, and so on. Thus, to grouped according to these units. Ancient remains are buried at understand Buyeo’s ancient topography, it is necessary to depths between 0 to 1 m in the granite, whereas they are found understand the sequence of these natural changes using a map between 2 to 4 m in alluvial land. Consequently, it is predating the 1970s that does not contain artificial geomorphic hypothesized that there no significant topographic change changes. Here, a contour map of the year 1918 (scale: 1/25,000) occurred in the granite areas during the last 1,500 years. is selected, because it includes a large amount of data and

This contribution has been peer-reviewed. The double-blind peer-review was conducted on the basis of the full paper. doi:10.5194/isprsannals-II-5-W3-301-2015 302

ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume II-5/W3, 2015 25th International CIPA Symposium 2015, 31 August – 04 September 2015, Taipei, Taiwan

Therefore, restoration should focus only the on alluvial covered areas.

Figure 3. Wang-Heung temple ruins and the relative position of the ancient water level

Meanwhile, the ancient climate during these times was warmer time of the temple’s construction, since capital cities of the and more humid than it is today, and the sea level was 6–7 m Baekje Dynasty were located near many large rivers, and the higher. This information is acquired from an analysis report on temple was constructed about 60 years after the establishment ancient breakwater ruins near the target area 60 km from the of the last capital city. Indeed, the ancient dock facility of the Yellow Sea as well as from the analysis of plant remains. The Wang-Heung temple site contains two water levels, adapted for target area was located within a river-flow distance and was the low- and high-level seasons. In addition, according to a affected by sea tidal action before the estuary dam construction Korean government analytic report, the overall river gradient in the 1980s. As a result, during high tides, the river flowed value for the target area to be restored ranges from 1/5,000 to slowly or even stopped, but at low tides, the river flowed very 1/8,000. There are two flood areas within the ancient city limits, fast. Because the target area is located on the marginal point of which were created during floods owing to the poor drainage tidal river, the upper river of the city shows in order. On the system. Lakes, where mud or clay layers were accumulated contrary, in the lower region, several sedimentation sequences during ancient times, existed in these areas before the ancient are observed, which produced a thick sedimentary unit. The city was constructed, suggesting that ancient river inundation width of the present river reaches 300 m. During the dry season, during the flooding seasons transformed the lowstand areas into ships cannot cross the river because the riverbed is exposed. wetlands. Therefore, the plain areas were unsuitable for However, as per older records and legends, the river was the construction but could be used as rice fields as they were rich in principal route for the ancient city. Hence, it seems that the river nutrients. Furthermore, the bank ruins excavated near one of the water level has declined during the last 1,500 years. According ancient lakes suggest that the natural lake was used as an to this assumption, the investigation of the ruins on the ancient artificial pond. riverside area led to the discovery of the Wang-Heung temple site, located 350 m from the river and at the foot of a mountain. 3.3 The ancient plain of Buyeo It contains some stonework ruins that probably functioned as an artificial bank and docking facility. On the basis of an old To reconstruct the ancient topography, the alluvial covered record, a Baekje king entered the temple by a ship. Hence, areas are divided into five groups (A–E), considering the river knowledge of the water level variability was available at the and seawater influence. The ancient topography is restored

Figure 4. Ancient topographic analysis around the alluvial areas

This contribution has been peer-reviewed. The double-blind peer-review was conducted on the basis of the full paper. doi:10.5194/isprsannals-II-5-W3-301-2015 303

ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume II-5/W3, 2015 25th International CIPA Symposium 2015, 31 August – 04 September 2015, Taipei, Taiwan using the burial depth values acquired from the excavation to the starting and ending points of the stonework at the Wang- report. However, the control points of the ancient surface are Heung temple site, and the average river gradient of 1/6,500 is too few to allow accurate estimates through GIS interpolation. applied. During the normal and flooding seasons, in the north Therefore, this study proposes a new method that converts point part of the target map, the water level corresponds to 6 and 9 m, to linear values. From a cross-section of the alluvial areas, the respectively. In the southeast part, the water level becomes 4.5 sedimentary thickness of the meeting point between the alluvial and 7.5 m, respectively. Appling these data to the GIS, the and river terrace of the backward mountain is almost zero, and ancient normal and flooding season topographic model the center point of the alluvial exhibits the greatest thickness. produced is shown in Figures 6 and 7. The ancient river By this simple principle, the center point of the alluvial is received greater water input and was formed more toward the calculated through a proportional equation using excavation inner part of the land than it is today. During the flooding data, two meeting points with the backward mountain, and the season, river water penetrates into even some parts of the mean gradient in both sides of the mountains acquired from GIS present downtown of Buyeo, and almost all of the lower alluvial spatial analysis. Subsequently, each cross-section diagram that area was inundated. The lower land was very wet because of the contains a center point burial and a location value is combined annual flooding. This correlates with old Chinese records. In with a branch-type line on the plain. Thus, the sediment addition, the descended folk story, which has been disregarded thickness is maximum at the center of the alluvial area. Figure 5 before as impossible on the basis of the present topography, is presents a 3D topography model of the ancient topography concordant with the restoration models. The old city buried using GIS and the center lines of five alluvial areas. inside the historic city Buyeo has been regarded as a well- ordered grid-type city, as viewed from the present topography, irrespective of the geological features. However, the assumed uneven surface morphology and humid condition question this hypothesis, proving it necessary to consider the restoration model.

3.5 Ancient steams and urban structure

Streams on the restored model can be analyzed with the GIS hydrology analysis tool. The ancient natural waterways make it clearer to interpret historic remains in order to understand the ancient land use and the administrative district divisions of the old city. In the ancient capital city of Buyeo, there were four collecting basins. Therefore, the existing excavated ruins should be reconsidered and reinterpreted in view of the restored topography and identified streams. Figure 8 presents an example of this new interpretation method. This area receives a considerable amount of water from the mountains in the east. Figure 5. A restoration model of the ancient plain The plain area includes an ancient rampart across the steam basin, with the moat evident outside the wall ruins. Indeed,

there are abundant water resources in this area, especially wider 3.4 The ancient river of Buyeo wall ruins than in the other plain ramparts. The evidence that The ancient river boundary is simply produced by filling the 3D the wall contacted directly with water suggests that the wall model with water. The standard ancient water levels correspond functioned as a bank facility. The rice field was supplied with

Figure 6. Ancient river boundaries during the normal tide Figure 7. Ancient river boundaries during the flood season season (water level is 6–4.5 m) (water level is 9–7.5 m)

This contribution has been peer-reviewed. The double-blind peer-review was conducted on the basis of the full paper. doi:10.5194/isprsannals-II-5-W3-301-2015 304

ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume II-5/W3, 2015 25th International CIPA Symposium 2015, 31 August – 04 September 2015, Taipei, Taiwan

field. Even the downtown area of Buyeo that has been regarded as the central region of Sabi capital city was in fact a paddy field in ancient times. The dwelling area was rather located on the inclined plane of the mountain valley, which has never been considered and excavated thus far. The present results indicate that in order to research a historic city properly, a topographic restoration is necessary. It provides researchers with complementary data to the existing study method and a precise analytical background. Furthermore, it reduces misconceptions and misinterpretations, which result from viewing only the present topography. In conclusion, it is expected that the topography restoration may aid in more efficient excavation plans and overcome the problem between conservation and development in historic cities.

REFERENCES

Figure 8. An example of the new hypothesis deducted from Buyeogun, 2009. The Baekma River, Buyeo, Korea. comparative analysis between the restored topography and the existing ruins Chungcheongnam-do history and culture center, 2007. Architecture and Civil Engineering of Baekje, Chungcheongnam-do history and culture center, Kongju, Korea. continuous water from the reservoir outside the western bank. Cho, W.C., 2011. Architecture and civil engineering of Baekje, The presented results (Figure 9) and a reinterpretation of the Seokyeonmuwhasa, Seoul, Korea. existing ruins suggest that the ancient topography of Buyeo was different from the present one; the previously assumed Gong, W.S. et al., 2011. Korean ancient paddy fields and rectangular grid-type urban structure does not coincide with the irrigation facilities, Seogyeongmunhwasa, Seoul, Korea. restored topography. The lower area that supposedly had annual inundation was used as a rice field, and most structures were Hong, S.J., 1956. The Legend of Baekje, Tongmunkwan, Seoul, constructed above 10 m from the sea level. A dwelling site is Korea. now located for the first time on the mountain slope. The area underneath the present-day downtown Buyeo, which was Kim, J.Y. et al., 2005. Stratigraphy of wetland depositional assumed to hold significant ancient remains, was in fact a rice sequence in Keum River Basin, Korea focused on Gungnamji, field and commercial site. Therefore, the new data provided Sorori and Naeheungdong areas. Journal of the Hoseo here call for new excavation plans for the restoration of the Archaeological Society, 13(-), pp. 5-54. historic city to progress further. Kim, Y.O., 1989. Korean Climate and Culture, Publishing department of Ewha Women's University, Seoul, Korea.

Korean Archeological Environment Labolatory et al., 2010. Korean Ancient Paddy Agriculture and Irrigation Facilityies, Seokyeongmoonhwasa, Seoul, Korea.

Kwon, H.J., 1975. A geographical study on the alluvial landforms of the Honam plain, Korea. Journal of the Korean Geographical Society, 10(2), pp. 1-20.

Lee, B.H., 2002. The expansion and development of the Baekje capital city Sabi-Doseong, Hankooksaron, 47(-), pp. 59-126.

Yoon, Y. et al., 1994. Joseon Folk Story, Hankukmunhwasa, Seoul, Korea.

Figure 9. Land use in the ancient capital city, Sabi of Buyeo

4. CONCLUSION

Buyeo has undergone significant topographic changes from 663 AD until today. The reconstruction of the ancient topography reveals that the river was much wider and higher than today, and that substantial part of today urban areas were part of the river in the past. Contrary to former belief, the Sabi capital city was planned and constructed, adapting to the ancient geomorphic context. The lowland was inundated annually; therefore, it was used as a rice

This contribution has been peer-reviewed. The double-blind peer-review was conducted on the basis of the full paper. doi:10.5194/isprsannals-II-5-W3-301-2015 305